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Buckthorn Beware!

Friends of the Blufflands is conducting a study of common buckthorn, an invasive shrub that has infested many of the forests and prairies of the Upper Midwest, including Hixon Forest. It is known that cutting buckthorn without treating the stump with an herbicide causes it to resprout often with multiple stems. It is not well known how frequent and for how long buckthorn must be cut for it to die and not resprout. We seek to help answer this question by sectioning off an area in Hixon Forest with heavy growth of buckthorn and cutting different parts of that section at different frequencies for as long as it takes to see no further resprouts. We hope to be able to determine the optimum time and frequency that buckthorn needs to be cut as a way to eliminate it without the use of herbicides.

Hypothesis- It will take many cuts at an unknown frequency for at least one growing season to eliminate buckthorn.

Methods- A 10 x 40 feet plot will be marked off and divided into 4 sections each measuring 10 x 10 feet. This plot will be chosen for its uniformity of buckthorn growth. The four sections will be arranged such that they are side-by-side along the slope and up the slope from bottom to top. These sections will be cut as close to the ground as possible at 4 different frequencies, every 2 weeks, 4 weeks, 6 weeks and 8 weeks, until no resprouts are seen. A border will be cut around this 10 X 40 foot plot. The nearby uncut buckthorn will be used as a control and a nearby 10 x 10 plot will be cut and treated with herbicide in the traditional way.

The first cutting of the entire plot took place on June 16 with a brush cutter with a blade. June 16 was chosen because much of the energy from the roots will have been invested into plant and leaf growth by that time with relatively little regeneration of the root energy from photosynthesis. Subsequent cuttings were done from that date as per the following schedule. It is recognized that new seedlings from the seed bank will appear and have to be taken into consideration. A 15 x 50 feet section on Lookout savanna located in an area relatively easily accessible from Savanna Trail was chosen for its uniform growth of buckthorn. The buckthorn was about waist to shoulder tall with the diameter of stems mostly under 0.5 inch with some up to one inch. There were minimal other woody plants present, such as honeysuckle or oriental bittersweet. This area was cut with a brush cutter with a blade close to the ground, the cut stems were gathered and removed from the area, then a second pass was made with the brush cutter to assure that all the stems were cut. Then 4 side-by-side 10 x 10 feet areas were staked out within this 15 x 50 foot area. Down the slope and separated from the 15 x 50 area by a 3-4 foot cut buffer, a second 10 x 10 area had all the woody plants removed with the traditional cut and treat method using hand held pruners and 20% triclopyr in bark oil.

Here are photos:

View of area looking east before cutting

View of area looking west before cutting

Area looking west after cutting

Typical cut stems

Four 10 x 10 feet sections marked off side-by-side

A 10 x 10 feet section below the main 15 x 50 area, with a 3-4 foot cut buffer between them,

where all stems were cut and treated (Triclopyr 4, 20%, in bark oil with blue dye).

Typical stems that were cut and treated

The plan will be to recut section #1 every 2 weeks, #2 every 4 weeks, #3 every 6 weeks, and #4 every 8 weeks.

Here is a schedule for when each section will be cut:

On 9/8/22, Lauren Brochtrup, a student at the University of Wisconsin La Crosse, joined the project as part of an Environmental Studies Capstone Project.

The results of this study will be published on this blog when completed. We hope it provides valuable information to us and others.

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This is very interesting, and I look forward to seeing the results. It would be great to figure out a way to avoid having to treat the cut stumps. I'm curious about another thing to try—cutting and then covering the area with black plastic or something else impermeable to water or sunlight. I tried that on a couple of fairly big tree stumps and it took a while but did seem to prevent them from resprouting. Of course this wouldn't work in situations where the buckthorn plants occurred just here and there.


We need more studies like this: well planned, set up to answer a specific question, and generating results that can be used. Kudos!

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